Process integration for embedded silicon/silicon oxide/silicon nitride/silicon oxide/silicon (SONOS) technology is an area of interest for the electronics industry. Embedded SONOS technology typically includes the formation of input/output (I/O) regions between non-volatile memory regions and core/logic regions. This embedded SONOS arrangement is found in many of today's integrated circuit systems such as, cellphones, portable music players, video cameras, and computers.
Central to many integrated circuit system processes, including SONOS processes, is the formation of a silicon nitride (Si3N4) layer. Silicon nitride is often used as a passivation layer, a mask material, and/or a charge trapping layer. Regardless of its chosen application, the silicon nitride film should display a high film purity and density, uniform stoichiometry, and a uniform thickness. Low pressure chemical vapor deposition (LPCVD) has emerged as the process for depositing silicon nitride films with superior properties.
Despite LPCVD advancements, silicon nitride is still subject to discontinuities such as pinhole formation. These pinhole formations not only affect the integrity of the silicon nitride layers themselves, but they also may affect adjacent layers as well. For instance, during the removal of a silicon oxide/silicon nitride/silicon oxide (ONO) layer, dry etching of the top silicon oxide layer, followed by a wet clean step, may attack the bottom silicon oxide layer through the pinholes within the silicon nitride layer. This erosion of the bottom silicon oxide can lead to silicon substrate pitting during the dry etch of the silicon nitride layer. Pitting of the silicon substrate can lead to gate dielectric failure during subsequent gate dielectric formation.
Thus, a need still remains for the forming of a defect free silicon nitride layer or the processing of a silicon nitride layer without defect formation. In view of the ever-increasing need to save costs and improve efficiencies, it is more and more critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.